Solar Wind and Internally Driven Dynamics: Influences on Magnetodiscs and Auroral Responses

Delamere, P. A.; Bagenal, F.; Paranicas, C.; Masters, A.; Radioti, Aikaterini; Bonfond, Bertrand; Ray, L. C.; Jia, Xianzhe; Nichols, J. D.; Arridge, C. S.

doi:10.1007/s11214-014-0075-1

Cited by 47 publications

(35 citation statements)

References 194 publications

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“…The dynamics of the giant‐planet magnetospheres are strongly influenced by planetary rotation. The moons of Jupiter and Saturn, Io and Enceladus, respectively, feed plasma into rotating magnetodiscs composed of equatorially confined plasma, carrying currents that distort the magnetic field into a disc‐like structure (see reviews by Kivelson [] and Delamere et al []). The magnetodisc can be described with a two‐dimensional equilibrium model [e.g., Caudal , ; Achilleos et al , ; Chou and Cheng , ] where a current sheet forms in the middle magnetosphere and a more dipolar field forms in the outer magnetosphere (hereafter defined as the magnetic cushion).…”

Section: Introductionmentioning

confidence: 99%

Magnetic flux circulation in the rotationally driven giant magnetospheres

et al. 2015

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The giant‐planet magnetodiscs are shaped by the radial transport of plasma originating in the inner magnetosphere. Magnetic flux transport is a key aspect of the stretched magnetic field configuration of the magnetodisc. While net mass transport is outward (ultimately lost to the solar wind), magnetic flux conservation requires a balanced two‐way transport process. Magnetic reconnection is a critical aspect of the balanced flux transport. We present a comprehensive analysis of current sheet crossings in Saturn's magnetosphere using Cassini magnetometer data from 2004 to 2012 in an attempt to quantify the circulation of magnetic flux, emphasizing local time dependence. A key property of flux transport is the azimuthal bend forward or bend back of the magnetic field. The bend back configuration is an expected property of the magnetodisc with net mass outflow, but the bend forward configuration can be achieved with the rapid inward motion of mostly empty flux tubes following reconnection. We find a strong local time dependence for the bend forward cases, localized mostly in the postnoon sector, indicating that much of the flux‐conserving reconnection occurs in the subsolar and dusk sector. We suggest that the reconnection occur in a complex and patchy network of reconnection sites, supporting the idea that plasma can be lost on small scales through a “drizzle”‐like process. Auroral implications for the observed flux circulation will also be presented.

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Section: Introductionmentioning

confidence: 99%

Magnetic flux circulation in the rotationally driven giant magnetospheres

et al. 2015

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“…The giant magnetospheres (i.e., Jupiter's and Saturn's magnetospheres) are characterized by several internal plasma sources and fast planetary rotation [ Delamere et al , , and references therein]. A steady state magnetosphere model implies an outward radial transport of this plasma.…”

Section: Introductionmentioning

confidence: 99%

“…Galileo observed several intermittent, short‐duration (i.e., ≈ 26 s) events of increased magnetic field magnitude (i.e., ≈ 1%) and with no ion cyclotron waves near Io, which have been interpreted as narrow channels of fast (i.e., ≈ 100 km s) inward motion of tenuous plasma (i.e., ≈ 100 cm −3 ) [ Thorne et al , ; Kivelson et al , ]. For Saturn, about 70–750 kg s −1 of water vapor is ejected from Enceladus' geysers and about 12–250 kg s −1 of that is ionized and transported radially outward [ Bagenal and Delamere , ; Delamere et al , ]. So‐called “injection” events have often been observed by Cassini in Saturn's inner magnetosphere, characterized by a short interaction with a hot tenuous plasma embedded within an ambient cold and dense plasma [ Krimigis et al , ; Mauk et al , ; Thomsen , , and references therein].…”

Section: Introductionmentioning

confidence: 99%

Plasma transport driven by the Rayleigh‐Taylor instability

Delamere

Otto

2016

JGR Space Physics

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Two important differences between the giant magnetospheres (i.e., Jupiter's and Saturn's magnetospheres) and the terrestrial magnetosphere are the internal plasma sources and the fast planetary rotation. Thus, there must be a radially outward flow to transport the plasma to avoid infinite accumulation of plasma. This radial outflow also carries the magnetic flux away from the inner magnetosphere due to the frozen‐in condition. As such, there also must be a radial inward flow to refill the magnetic flux in the inner magnetosphere. Due to the similarity between Rayleigh‐Taylor (RT) instability and the centrifugal instability, we use a three‐dimensional RT instability to demonstrate that an interchange instability can form a convection flow pattern, locally twisting the magnetic flux, consequently forming a pair of high‐latitude reconnection sites. This process exchanges a part of the flux tube, thereby transporting the plasma radially outward without requiring significant latitudinal convection of magnetic flux in the ionosphere.

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“…The aurorae at Jupiter consist of several distinct features of various sizes, shapes, and locations (see reviews by Grodent, 2015;Delamere et al, 2014, and references therein). Studies dedicated to specific features confirmed that their generation mechanisms are indeed different and, to a large extent, independent.…”

Section: Introductionmentioning

confidence: 99%

The far-ultraviolet main auroral emission at Jupiter – Part 1: Dawn–dusk brightness asymmetries

Bonfond¹,

Gustin²,

Gérard³

et al. 2015

Ann. Geophys.

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Abstract. The main auroral emission at Jupiter generally appears as a quasi-closed curtain centered around the magnetic pole. This auroral feature, which accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range, is related to corotation enforcement currents in the middle magnetosphere. Early models for these currents assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use far-UV images from the Hubble Space Telescope to further characterize these variations on a statistical basis. We show that the dusk side sector is ∼ 3 times brighter than the dawn side in the southern hemisphere and ∼ 1.1 brighter in the northern hemisphere, where the magnetic anomaly complicates the interpretation of the measurements. We suggest that such an asymmetry between the dawn and the dusk sectors could be the result of a partial ring current in the nightside magnetosphere.

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Solar Wind and Internally Driven Dynamics: Influences on Magnetodiscs and Auroral Responses

Cited by 47 publications

References 194 publications

Magnetic flux circulation in the rotationally driven giant magnetospheres

Magnetic flux circulation in the rotationally driven giant magnetospheres

Plasma transport driven by the Rayleigh‐Taylor instability

The far-ultraviolet main auroral emission at Jupiter – Part 1: Dawn–dusk brightness asymmetries

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